This invention is directed to an environmentally friendly cleaning agent, and more particularly to a cleaning agent which is a volatile methyl siloxane containing binary azeotrope.
Because of local, state, federal, and international regulations, aimed at restricting the use of certain chemicals, the search for suitable replacements is an ever increasing dilemma faced by the chemical and industrial sectors. The magnitude of the problem is exemplified below.
In the 1970s for instance, the US Environmental Protection Agency (EPA) named as criteria or "hazardous pollutants" sulfur dioxide SO.sub.2 ; carbon monoxide CO; nitrogen dioxide NO.sub.2 ; ozone O.sub.3 ; suspended particulate with a diameter of ten microns (micrometers) or less PM.sub.10 ; lead Pb; and nonmethane hydrocarbons (NMHC) now known as "volatile organic compounds" (VOC).
The most abundant species of photochemical smog is ozone. Ozone precursors are VOC, nitric oxide NO, and NO.sub.2. In order to reduce ozone in a polluted atmosphere, reductions in VOC and nitrogen oxide NO.sub.x (NO and NO.sub.2) precursors has been required.
Solar energy is absorbed by the surface of the earth and re-emitted as radiation. Certain gases in the atmosphere are capable of absorbing the re-emitted radiation and translating it into heat (THE GREENHOUSE EFFECT). The result is a higher atmospheric temperature (GLOBAL WARMING) than would be obtained in the absence of these "GREENHOUSE GASES". Accordingly, reductions in the emission of such gases has also been required, including carbon dioxide CO.sub.2, methane CH.sub.4, nitrous oxide N.sub.2 O, ozone, and a variety of chloro, fluoro, and chlorofluorocarbons (CFC) such as methylchloroform CH.sub.3 CCl.sub.3 (MCF), carbon tetrachloride CCl.sub.4, C.sub.2 HF.sub.5 (HCFC-125), C.sub.2 H.sub.2 F.sub.4 (HFC-134a), and chlorofluorocarbons such as CFCl.sub.3 (CFC-11), CF.sub.2 Cl.sub.2 (CFC-12), C.sub.2 ClF.sub.5 (CFC-115), CHClF.sub.2 (HCFC-22), C.sub.2 HCl.sub.2 F.sub.3 (HCFC-123), C.sub.2 HClF.sub.4 (HCFC-124), and C.sub.2 Cl.sub.3 F.sub.3 (CFC-113).
Stratospheric ozone is a natural shield against the penetration of uv-light in the rays of the sun. There has been concern that any process which depletes stratospheric ozone will increase the amount of uv-B radiation (293-320 nanometers/2930-3200 angstroms) reaching the surface of the earth. Increased uv-B radiation may lead to the increased incidence of skin cancer. CFC's diffuse through the troposphere (up to 10 miles/16 kilometers) and into the mid-stratosphere (up to 30 miles/48 kilometers), where they are photolyzed by uv radiation and destroy ozone molecules. Because of STRATOSPHERIC OZONE DEPLETION, mandates such as the 1990 Clean Air Act Amendment contain a phaseout schedule for CFC's, halons (bromochlorofluorocarbons and bromofluorocarbons), carbon tetrachloride, and methylchloroform.
These are only a few of the problems faced by the chemical and industrial sectors in finding suitable replacements for such chemicals. Of particular interest according to the present invention, however, is the VOC aspect of the problem and the provision of a suitable substitute material. The solution to that problem is the object of the invention.
Thus, "volatile organic compounds" (VOC) and "volatile organic material" (VOM) are defined in the United States by Federal statute in Title 40 CFR 51.100(s) to be any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions. The definition excludes certain compounds and classes of compounds as VOC or VOM.
Scientifically, VOC has been defined as any compound of carbon that has a vapor pressure greater than 0.1 millimeters of mercury (13.3 Pa) at a temperature of twenty degrees Centigrade and a pressure of 760 millimeters mercury (101.3 kPa); or if the vapor pressure is unknown, a compound with less than twelve carbon atoms. "Volatile organic content" is the amount of volatile organic compounds (VOC) as determined according to EPA Test Method 24 or 24A, the procedures of which are set forth in detail in Title 40 CFR Part 60, Appendix A.
Reduction of VOC has already been mandated in several states, and regulations in California for example, require less than about 180 grams of volatile material per liter of any product which enters the atmosphere. This amount can be determined by baking ten grams of a product in an oven at 110 degrees Centigrade for one hour. The amount of solids which remain is subtracted from the total of the ten grams which was tested. Calculations are based on the weight of the volatile that have evaporated, and the amount is reported as grams per liter.
The EPA has identified many volatile organic compounds (VOC) present in consumer products among which are such common solvents as ethanol, isopropyl alcohol, kerosene, and propylene glycol; and common hydrocarbon solvents such as isobutane, butane, and propane, which are often employed as propellants in various aerosol sprays.
The state of California under the auspices of the California Air Regulation Board (CARB), has proposed standards which would limit and reduce the amount of volatile organic compounds (VOC) permitted in various chemically formulated products used by household and institutional consumers. These regulations cover products such as detergents; cleaning compounds; polishes; floor products; cosmetics; personal care products; home, lawn and garden products; disinfectants; sanitizers; and automotive specialty products.
These CARB type standards would effect such widely used common consumer products such as shaving lather, hair spray, shampoos, colognes, perfumes, aftershave lotions, deodorants, antiperspirants, suntan preparations, breath fresheners, and room deodorants.
Replacement of "outlawed" chemicals with certain volatile methyl siloxanes (VMS) as a solvent substitute is a viable approach. In fact, the EPA in Volume 59, No. 53, of the Federal Register, 13044-13161, (Mar. 18, 1994), has indicated at Page 13091 that "Cyclic and linear volatile methyl siloxanes (VMSs) are currently undergoing investigation for use as substitutes for Class I compounds in metals, electronic and precision cleaning. Because of their chemical properties, these compounds show promise as substitutes for cleaning precision guidance equipment in the defense and aerospace industries. In addition, the volatile methyl siloxanes have high purity and are therefore relatively easy to recover and recycle. In the cleaning system using VMSs, the fluids are used to clean parts in a closed header system using a totally enclosed process. The parts are drained and then dried using vacuum baking".
At Pages 13093-13094, the EPA goes on to state that the "volatile methyl siloxanes dodecamethylcyclohexasiloxane, hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane are acceptable substitutes for CFC-113 and MCF" for cleaning in closed systems, in the metals cleaning sector, the electronics cleaning sector, and the precision cleaning sector; under the EPA Significant New Alternatives Policy (SNAP).
At Page 13137, the EPA notes that with regard to the two volatile methyl siloxanes octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane, the "Agency has completed review of data, and intends under separate rule-making to propose these chemicals as acceptable with the use condition that the company-set exposure limits must be met".
In addition, a petition to the EPA filed in late 1992 is pending seeking exemption of these volatile methyl siloxanes (VMS) from regulation as VOC. The basis for the petition is that the volatile methyl siloxanes do not contribute to, and in some cases actually inhibit the formation of tropospheric ozone. Thus, the volatile methyl siloxanes have a lower ozone formation potential than ethane, which is the most reactive compound on a list of "exempt" VOC.
Furthermore, these volatile methyl siloxanes (VMS) have an atmospheric lifetime of between 10 to 30 days. As a consequence, VMS compounds do not contribute significantly to global warming. Volatile methyl siloxanes have no potential to deplete stratospheric ozone due to their short atmospheric lifetimes so that they will not rise and accumulate in the stratosphere. VMS compounds also contain no chlorine or bromine atoms.
Volatile methyl siloxane compounds (VMS) neither attack the ozone layer nor do they contribute to tropospheric ozone formation (Smog), and they have minimum GLOBAL WARMING potential. Volatile methyl siloxane compounds are hence unique in simultaneously possessing these three attributes.
Thus, it should be apparent that volatile methyl siloxanes provide a viable solution to the problem of finding a suitable replacement for "outlawed" chemicals heretofore commonly used as cleaning agents.